How can I format the serial number on the invoices, change the packing list to a delivery note, and add the carton quantity to it ?

Welcome to the Community, nk6.

Let me break down your questions so I can make sure I am covering everything.

For your first question, you can manage the format of your serial number by going to the Product/Service information of the item. I'll walk you through how below:

1. Go to the Gear icon and choose Products and services.
2. Choose a product you want to format the serial number (SKU). Then, click Edit.
3. Enter the serial number from the SKU field with your desired format.
   
4. Click Save and close.

Learn more about adding inventory products including SKU's in QBO (Instructions are outlined in Step 2 of this article): Add inventory products in QuickBooks Online.

For your next question about changing the packing list to a delivery note, there's no way to directly change that. QuickBooks Online (QBO) uses the term Packing List/Slip also known as Delivery Notes based on which country you're using when you sign up your account. For United States version, it is defaulted as Packing slip. Other countries uses Delivery Notes as their default term.

For your final question, adding carton quality on packing slip or delivery note is not yet possible in QBO. This is a good idea that our engineers would love to know about.

In the meantime, I want you to stay updated with the latest features available in the product through our QuickBooks Blog.

Get back to me if you have other questions. I'm always happy to help you further. Keep safe and have a great rest of the day!